Furnace grate and air supply therefor



D. R. PEARL May 20, 1969 FURNACE GRATE AND AIR SUPPLY THEREFOR Filed Aug. 24, 1967 Sheet INVENTOR. DAVID E. PEARL Av-ramvsy y 0, 1969 D. R. PEARL 3,444,831

FURNACE GRATE AND AIR SUPPLY THEREFOR Filed Aug. 24, 1967 Sheet 4? of 2 FIG-3 l NVENTOR.

DAVID E- PEARL ATTOIZNE) United States Patent "ice FURNACE GRATE AND AIR SUPPLY THEREFOR David R. Pearl, West Hartford, Conn., assignor to Combustion Engineering, Inc., Windsor, Conn, 21 corporation of Delaware Filed Aug. 24, 1967, Ser. No. 663,130 Int. Cl. F23b 1/22; F2311 11/00; F23g /00 US. Cl. 11033 4 Claims ABSTRACT OF THE DISCLOSURE An incinerator furnace for burning refuse having an inertial grate for causing the burning refuse to move from the inlet end to the ash discharge end of the grate. The grate is mounted on leaf springs, and a motor pulls the grate towards its inlet end and releases it suddenly so that the action of the leaf springs causes it to move toward its original position until it comes into contact with a stop member. The inertia of the burning refuse moves it along the grate. The grate plates are held in place on a support member by a hooking arrangement to prevent them from being jarred out of place. The air duct for supplying underfire air is integral with the grate so that ash particles falling thereinto will also be moved towards the discharge end of the grate.

Background of the invention The invention relates to an incinerator furnace for burning refuse therein. Some incinerators today use an inertial grate for causing the burning refuse to move from the inlet end to the ash discharge end of the grate. The jarring action of the grate when it comes into contact with the stop member causes some problems in that it tends to loosen and displace the grate plates on the support member. Problems are also encountered in removing the ash siftings from the air duct which is positioned beneath the grate for supplying it with underfire combustion air.

Summary of the invention The inertial grate of my invention incorporates an underfire air duct which is made integral with the grate, so that ash particles falling down into the air duct are moved along the length of the air duct to the discharge end. The front end of the grate is adjustable vertically, to change the angle of the grate, so that the rate of travel of the burning refuse can be changed, depending on the characteristics of the refuse. The loosely supported grate plates contain a portion on their front edges which are positioned beneath hooked members on the support, so that the jarring action of the grate does not displace them, yet permits them to be readily lifted out of their bed. The loose support is of no particular advantage in and by itself. The novel feature is to support the grate plates without screws, nuts, pins or similar fasteners which might be damaged by heat and become difficult to remove for servicing of the grate.

Brief description of the drawings FIGURE 1 is a cross sectional side elevation of an incinerator furnace grate constructed in accordance with my invention;

FIGURE 2 is a sectional view of the furnace grate taken on line 2-2 of FIGURE 1; and

FIGURE 3 is a top view of the grate taken on line 3-3 of FIGURE 1.

Description of the preferred embodiment Looking now to FIGURE 1 of the drawings, designates an incinerator stoker in its entirety. Located in the Patented May 20, 1969 lower portion of the furnace is an inertial grate 12, upon which the burning refuse rests. Refuse is introduced through the front wall of the furnace by way of opening 11, and after completing its travel through the furnace, ash is discharged from the back end of the grate 12 into a water-filled ash pit 44.

The fuel is caused to travel along the length of the grate bed by means of inertia imparted to it by a forward and backward movement of the grate bed, in conjunction with a stop member for causing abrupt stopping of the forward movement of the grate. The inertia imparted to the fuel bed causes it to travel a distance along the grate during each forward and backward movement. The grate 12 is mounted on a plurality of leaf springs 14 located at each of the four corners of the grate. Addition or removal of the number of leaves may be used to vary the spring constant, and hence the inertial shock capabilities of the grate.

A piston-cylinder arrangement 18 and 20 is used to move the grate to the left as shown in FIGURE 1, against the action of the leaf springs 14. Rod 22 is connected to the piston 20 at one of its ends, and is fastened to the grate 12 at its other end. Rod 22 also carries a stop member 28, which coacts with stop member 30 which is suitably affixed to stationary structure for causing abrupt stopping of the grate during its forward motion. Stop member 30 has a flexible pad 32 attached thereto, for the purpose of preventing damage to the apparatus from the pounding of the stop members. Air is introduced into the cylinder through inlet line 24, and is exhausted from this chamber by way of outlet line 26. Hydraulic or mechanical means could also be used to draw back and release the grate. The grate is made up of three integral tiers, the highest of which is adjacent to the front wall of the furnace. Thus as the refuse falls from one tier to the next some of it is turned over and agitated causing more intimate contact of the refuse and air.

Grate 12 is composed of a plurality of grate plates 34 which are loosely supported on a support bed made up of I-beam members 36 (FIGURES 1 and 2). The support bed further includes hook-shaped members 38 which serve the purpose of preventing the loose grate plates 34 from becoming dislodged during the jarring action of the grate. As best seen in FIGURE 1, each of the grate plates contain a tab 40 which slips in under the hooked portion of members 38. Although secured against dislodgement during operation, the grate plates may readily be lifted out of the bed for servicing or replacement by lifting the non-hooked end first.

In order to vary the speed at which the refuse travels, an adjustable device is provided for moving the front end of the grate in a vertical direction. The entire grate assembly is mounted on a metal bed 43, which is pivotable around axis 41. By loosening the nuts and turning bolts 42, which coact with threaded openings in foundation member 43, the front end of the grate bed 12 can be either raised or lowered as desired. By making such an adjustment, the angle of the grate bed is varied. Thus for example, if extremely wet garbage or refuse were being burned during a portion of the year, the front end of the grate 12 could be moved in a downward direction, so that a longer residence period within the furnace of the wet refuse is obtained. If, on the other hand, the bulk of the refuse would be fast burning in nature, i.e., discarded plastics, cardboard boxes, newspapers, etc., the front end of the grate could be adjusted upwardly. Thus the burning fuel would travel at a faster rate through the furnace.

Underfire combustion air is supplied to the underside of the grate by means of forced draft fan 46 and duct 48. Openings 52 in the grate plates permit the air to flow upwardly through the grate into contact with the burning refuse. Air duct 48 contains side walls 50 (FIGURE 2) which permits some of the combustion air to enter the furnace along the side walls thereof, thus cooling the side plates of the grate and protecting the furnace walls against slagging. An air seal plate 80 prevents air from flowing up between the front wall of the furnace and the stoker. Dampers 51 can be regulated to vary the air supply longitudinally along the grate bed. By the same token, dampers (not shown) can be provided for varying the amount of air flowing up along the side walls 50 in relation to the air flow through openings 52, if desired.

As is the case with any grate supplied with underfire air, siftings of ash and other small foreign particles may fall down into the air duct 48. In order to remove this ash, the air duct 48 is made integral with the grate 12. Thus the jarring action not only moves the burning fuel bed from the front end of the furnace to its discharge end but will also cause the ash particles in the bottom of the air duct 48 to travel in this direction. A damper 56 is positioned at the rear end of the air duct 48, for permitting the ash to be periodically discharged into the ash pit 44.

A flexible fabric or metal connection 54 is provided between the air duct 48 and the stationary fan 46. This flexible joint will permit horizontal movement of the air duct 48 along with grate 12 while the fan 46 remains motionless. The fan is mounted on the grate bed frame so that it rises with the grate during angle adjustment.

The operation of the grate will now be described. Refuse to be burned is introduced into the furnace through front wall opening 11 and falls down onto the grate 12. Air is introduced into cylinder 18 through line 24 causing the grate 12 to be pulled to the left. Inlet line 24 is then closed and outlet line 26 is opened. The spring action of leaf springs 14 then pulls the grate 12 in a rightward direction until stop member 28 comes into contact with coacting stop member 30. The inertia imparted to the burning refuse causes it to continue in a rearward, or right-hand direction. This forward and backward movement of the grate is repeated continuously with each cycle running approximately ten to twenty seconds. This causes the burning refuse to travel a few inches during each cycle.

The abrupt stopping of the grate by contact of stop members 28 and 30 may tend to lift the front end of each grate plate 34 upwardly. Without any provision for holding these plates 34 in place, many of them would be re-arranged during operation of the grate. Tabs 40, which slip in under hooked members 38, prevent the grate plates from being displaced. It is undesirable to fasten the grate plates 34 to the supports by means of bolts or screws, since they would be more costly and might jam from the high temperatures encountered thus presenting a maintenance problem. The grate plates 34 of the present invention can be quickly and easily assembled during initial construction and present very little maintenance. All of the grate plates 34 are slightly spaced from one another so that they are free to expand with heat. This slight spacing also permits the plates to be easily replaced when necessary. The grate plates along the side edges of the stoker have vertical sides (FIGURE 2) to retain the refuse and reduce scufiing and abrasion of the furnace walls.

The ash particles which sift down into air duct 48 are automatically moved from the front end of the unit to the rear end by the jarring action which the duct is subjected to. By means of bolts 42, the rate of travel of refuse through the furnace can be quickly and easily adjusted. Other adjustments in refuse travel may be achieved by varying the severity of the inertial shock by withdrawing the gate further to the rear on each stroke; or by varying the number of inertial strokes per minute.

While the preferred embodiment of the invention has been illustrated and described, it is to be understood that the invention should not be limited thereto.

What I claim is:

1. In a furnace for burning fuel therein, a grate for supporting burning fuel thereon, said grate having a front end upon which unburned fuel is deposited, and a back end from which ash is discharged, inertial means cooperating with the grate for causing said grate to move intermittently forward and backward, means for abruptly stopping the rearward movement of the grate, thus causing the fuel to progress from the front end to the back end of the grate as it burns, said grate comprising a plurality of grate plates, support means for supporting the grate plates, said support means including a plurality of hook members, each of the grate plates having means on its end which is closest to the front end of the grate for lying under the hook of the hook members, there being no other securing means for holding the grate plates in place on the support means, whereby the hook members prevent the grate plates frm being jarred out of place by the inertia imparted to the grate by the abrupt stopping thereof, means for raising and lowering the front end of the grate, whereby the speed at which the fuel traverses the grate can be varied, said grate being in the form of a plurality of vertically spaced tiers, the tiers being progressively higher from the back to the front of the grate, said tiers being integrally connected, so that as the fuel falls from one tier to the next, the fuel is agitated.

2. In a furnace for burning fuel therein, a grate having air openings therein for supporting burning fuel thereon, said grate having a front end upon which unburned fuel is deposited, and a back end from which ash is discharged, inertial means cooperating with the grate for causing said grate to move intermittently forward and backward, means for abruptly stopping the rearward movement of the grate, thus causing the fuel to progress from the front end to the back end of the grate as it burns, duct means extending beneath the grate for supplying underfire air up through the openings in the grate, said duct means being integrally connected to the grate, so that it moves intermittently forward and backward with the grate, whereby any ash or siftings which fall down into the duct will be moved from the front end to the rear end of the duct, and opening means at the rear end of the duct through which the ash can be removed.

3. The combination set forth in claim 2, including stationary fan means, flexible connecting means between the fan means and the duct, whereby the fan means remains stationary while the duct moves intermittently forward and backward, the discharge of the fan means being connected to the front end of the duct.

4. The combination set forth in claim 3, including means for raising and lowering the front end of the grate, whereby the speed at which the fuel traverses the grate can be varied.

References Cited UNITED STATES PATENTS 1,109,266 9/ 1914 Thacher 47 1,798,019 3/1931 Harrison 11032 1,939,177 12/1933 Losch 11038 XR 2,108,394 2/ 1938 Steinmuller 11033 2,338,027 12/1943 Davies 11032 3,356,204 12/ 1967 Kolberg 19859 XR FOREIGN PATENTS 550,915 1/ 1943 Great Britain. 686,590 1/ 1953 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner.

HARRY B. RAMEY, Assistant Examiner. 

